如何解决如何避免循环引用asp.net核心mvc [HttpPost“ add-recipe”] Web API
我的项目是.NET Core 5.0的食谱应用(烹饪)
我在添加新食谱(HttpPost)Web API时遇到问题
关于邮递员,我的答复是:
“检测到可能的对象循环。这可能是由于循环引起的,或者对象深度大于最大允许深度32。请考虑在JsonSerializerOptions上使用ReferenceHandler.Preserve支持循环。”
当我创建新食谱时,应使用recipeToCreateDto而不是包含所有属性(循环引用)的食谱
您能帮我如何使其正常运行吗?如何映射等
https://i.postimg.cc/Mphv7zRH/screen.png
我正在使用AutoMapper映射类和存储库模式。
public class AppUser
{
public int Id { get; set; }
public string UserName { get; set; }
public ICollection<Recipe> Recipes {get; set;}
}
}
用户有很多食谱。
public class Recipe
{
public int Id { get; set; }
public string Name { get; set; }
public AppUser AppUser { get; set; }
public int AppUserId { get; set; }
}
数据传输对象
public class RecipeForCreateDto
{
[Required]
[StringLength(50,MinimumLength = 3,ErrorMessage = "You must specify name between 3 and 50 characters")]
public string Name { get; set; }
public int AppUserId { get; set; }
public int AuthorId { get; set; }
}
在我的AutoMapperProfiles.cs中
public class AutoMapperProfiles : Profile
{
public AutoMapperProfiles()
{
CreateMap<RecipeForCreateDto,Recipe>();
}
配方界面
public interface IRecipeRepository
{
Task<Recipe> AddNewRecipe(Recipe recipe);
}
public class RecipeRepository : IRecipeRepository
{
private readonly DataContext _context;
private readonly IMapper _autoMapper;
public RecipeRepository(DataContext context,IMapper autoMapper)
{
_autoMapper = autoMapper;
_context = context;
}
public async Task<Recipe> AddNewRecipe(Recipe recipe)
{
await _context.Recipes.AddAsync(recipe);
await _context.SaveChangesAsync();
return recipe;
}
}
用户控制器:
User.GetUsername()是获取用户名的静态方法。
[HttpPost("add-recipe")]
public async Task<ActionResult> AddNewRecipe(RecipeForCreateDto recipeForCreateDto)
{
var userFromRepo = await _userRepository.GetUserByUsernameAsync(User.GetUsername());
recipeForCreateDto.Name = recipeForCreateDto.Name.ToLower();
if (await _recipeRepository.RecipeExists(recipeForCreateDto.Name))
return BadRequest("Recipe with that name already exists!");
var recipeToCreate = _autoMapper.Map<Recipe>(recipeForCreateDto);
recipeToCreate.AppUserId = userFromRepo.Id;
var createdRecipe = await _recipeRepository.AddNewRecipe(recipeToCreate); // here is problem
var recipeToReturn = _autoMapper.Map<RecipeForDetailDto>(createdRecipe);
return CreatedAtRoute("GetRecipe",new { controller = "Recipes",id = createdRecipe.Id },recipeToReturn);
}
解决方法
[HttpPost("{recipeForCreateDto}")]
public async Task < ActionResult > AddNewRecipe([FromBody] RecipeForCreateDto recipeForCreateDto) {
var userFromRepo = await _userRepository.GetUserByUsernameAsync(User.GetUsername());
recipeForCreateDto.Name = recipeForCreateDto.Name.ToLower();
if (await _recipeRepository.RecipeExists(recipeForCreateDto.Name)) return BadRequest("Recipe with that name already exists!");
var recipeToCreate = _autoMapper.Map < Recipe > (recipeForCreateDto);
recipeToCreate.AppUserId = userFromRepo.Id;
var createdRecipe = await _recipeRepository.AddNewRecipe(recipeToCreate); // here is problem
var recipeToReturn = _autoMapper.Map < RecipeForDetailDto > (createdRecipe);
return CreatedAtRoute("GetRecipe",new {
controller = "Recipes",id = createdRecipe.Id
},recipeToReturn);
}
,
“检测到可能的对象周期。这可能是由于 循环或对象深度大于最大允许深度 之32。考虑在以下位置使用ReferenceHandler.Preserve JsonSerializerOptions支持循环。”
对于此问题,您可以在startup.cs ConfigureServices
方法中添加以下代码:
services.AddControllersWithViews()
.AddNewtonsoftJson(options =>
options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
);
,
需要注意的是,.Net 中的默认序列化器现在来自 System.Text.Json.Serialization 命名空间。这个序列化器实际上在序列化和反序列化循环引用方面做得很好。
要启用此功能,请将以下代码放入您的 Startup.cs:
services
.AddControllers()
.AddJsonOptions(c => c.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.Preserve);
此处记录:https://docs.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-preserve-references
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